Apebble sinks in water a twig floats on top of the water compare the densities of the water, the pebble and the twig

A pebble that sinks in water has greater density than a twig floats on top of the water. A pebble has more mass in it and more compact compared to a twig. The water cannot easily penetrate the pores of the pebble unlike twigs. That is why pebbles have greater densities than twigs.

that tool is called an altimeter which measures your altitude which can be used to tell which atmosphere you are currently in, including the stratosphere.

hope this ! : )

reserve is the answer